1. Field of the Invention
The present invention relates to a structure for a nonlinear grating coupler, and particularly, to an improved structure for a nonlinear grating coupler which make it possible to provide a tapered nonlinear thin film and a stepped nonlinear thin film which are adaptable to an active optical connection implemented from a two-dimensional space to a third-order space.
2. Description of the Conventional Art
Various optical waveguide grating structures were introduced in the industry. The grating structure is generally formed on a linear and nonlinear optical waveguide. Here, the linear grating structure is widely used for a grating coupler, an optical interconnection, etc., and the nonlinear grating structure is widely used for a power-dependent grating coupler and an all-optical beam scanner. The grating-assisted directional coupler (GADC) of the linear and nonlinear grating structures has an advantages in that it can be used for a wavelength selective coupler for implementing the WDM.